This invention relates in general to a package articles and, more particularly, to a package of containers of the type customarily used for beverages including beer. Still more particularly, the invention relates to a packaging system for containers of multi-unit construction wherein there are provisions for substantial suppression of any flavor/taste imparting materials.
A number of different types of containers are employed in the beverage and food industry. As regards the carbonated and alcoholic containing beverages, metal containers or cans are extensively employed. The conventional drawn and ironed can consists of two components, namely a top and a can body. As known, in America the drawn and ironed two-piece can has largely replaced the three-piece can. The body portion of a two-piece can is generally made from aluminum or tinplated steel and is easily drawn into a cylindrical configuration and ironed down to a very thin wall thickness. Only the body is formed by a drawing and ironing procedure and when completed it includes a very thin side wall section and a domed end wall portion formed integrally with the side wall at one end thereof. The opposite end of the side wall is joined to a closure or can end which is usually double seamed thereon.
To produce can bodies, circular disks are stamped from metal sheet stock of the appropriate thickness. Each standard disk is drawn into a cup which is subsequently placed over a punch and forced through a die set where it is redrawn into a lesser diameter and ironed along its side wall to thereby substantially reduce the thickness of the side wall while at the same time elongating the side wall. The end wall, however, retains the original thickness of the metal sheet stock and, after the side wall is completely ironed, the punch drives the base against an end-forming die to impart a domed configuration. The domed structure enables the end wall to withstand high internal pressures without buckling outwardly and rendering the can body useable and giving it adequate column strength.
It has been the tendency to utilize thinner gauge metal stock which, in turn, produces yet still thinner side walls for containers. In production where rates often exceed several hundred per minute, cans are rapidly made by the so-called body making equipment. Thereafter, it is necessary to coat the external as well as the internal portions of the can structure. The external coatings are employed for reasons of protection and decoration, whereas the internal coatings serve mainly to protect the beverage or food ingredient from the metal surface of the container. The applied coatings are cured usually by heating and baking. Generally, the dry film thickness for the internal coating may range from about 2 to about 5 microinches when applied by a conventional spraying system. In the earlier coating systems an organic solvent was used and thereafter removed since the solvent only served as a carrier to convert the resins into a form suitable for application to the substrate. In recent times water-based coatings have been perfected and are extensively used for coating both food and beverage containers.
After the external and internal coatings are applied and cured the metal containers must be packaged in some convenient manner in order to transport or ship them to the concerns that will eventually fill the containers with beverage or food. In cans destined for the brewing industry, it is common practice to advance a unitized mass of containers onto a paperboard or chipboard structure or divider sheet stock and thereafter to place subsequent unitized masses of containers over such structures to build a tiered multi-unit package. Thus, large layers or tiers of metal containers are formed and may be readily bound by straps and thereafter shipped to the filling lines of the breweries. In practice, it has been observed in the use of paperboard, especially corrugated cardboard, that there is a propensity for various contaminating materials to cling to or collect upon the surface of such boards and, therefore, to impose or play some role in transferring unfavorable flavor/taste characteristics to the internal portions of coated metal containers. Seemingly, the contaminating materials are passed via migration or diffusion to the container walls and end up ultimately within the beverage or food product. This propensity to impart various contaminating materials or organoleptic active agents seem to be more prevalent with paperboard or chipboard, especially when such boards have been used a number of times in the shipping and handling process.
Actually, it is common practice in the industry to use the aforementioned boards four or more times in packing before they are finally discarded. In addition, moisture is readily absorbed by paperboard and it is believed that such moisture in combination with the cellulosic materials and the like that are formulated in making up such boards somehow contribute to the unfavorable flavor/taste phenomenon. Moreover, the various adhesives and binders used and their particular chemical constitutions apparently also contribute to this unfavorable situation. It may be mentioned that such conventional packaging arrangements are oftentimes placed in a warehouse prior to being used during storage. In such a condition, there may be temperature changes which contribute to the diffusion and migration of various chemical constituents from the paperboard or chipboard to the internal portions of the containers. As can be appreciated, there are ample opportunities for contaminating materials to find their way into the interior of cans and, thereafter, into the food or beverage that is eventually packaged therein.
While it is not known specifically the particular chemical constituents of the organoleptic active agents that act as contaminating materials which cause off-flavor or unfavorable flavor characteristics, a number of studies have been made which seem to indicate that such materials belong to the classes of organic compounds referred to as aldehydes and ketones. Qualitatively they influence taste or flavor even in trace concentrations, (in low parts per billion). Some of the materials that may be responsible for off-flavor include acetaldehyde, benzaldehyde, 2-nonenal and hexanal.
It is surprising that of the many possible candidates for use as plastic sheet material and, therefore, to function as divider sheet stock there are practically none that have been be found to be totally suitable. It will be appreciated that although a number of plastics or polymeric materials may have certain favorable properties as regards certain characteristics the same seemingly useful materials have other properties that make them unsuitable as plastic divider sheet stock. For example, certain plastics have the property of imparting or transferring a very small residue or film to the container surface, especially in contacting areas, such as around their open ends. The chemical makeup of such residual material may be of such a nature that there is a tendency, once transferred, to cause in a beer product the loss or reduction of its foamy head. This loss may often be traced to such materials as silicon-containing ingredients that are found in plastic sheet stocks employed for plastic divider stock. Such ingredients are often incorporated during polymerization to serve as an antiblocking agent as, for example, in the glycol-modified polyalkyleneterephthalate compositions and the like. Further, certain plastic sheet stock compositions may not actually impart any off-flavor or taste yet they may lack the proper surface characteristics, that is, they may have too little or too much resistance to sliding of the base portions of containers or cans. It is important that the surface properties of the sheet provide conditions at the interface between its plastic surface and the resin coated surface of the containers that are not too slippery. If the surface conditions are not right, particularly during the processing of advancing a plurality of containers onto the divider sheet or during their movement in subsequent shipping or handling, there is a marked tendency for the containers to slide outside the confines of the sheet and, therefore, fall or tumble resulting in a chaotic condition. Plastic materials such as the so-called high density polyethylenes as well as glycol-modified polyethyleneterephathalates exhibit this property. Further, certain plastic sheet materials are too brittle and lack the proper flexibility for transfer and manipulation. Related to this is brittleness and the tendency of some plastic materials in the form of divider sheets to split or crack with relative ease upon usage. Polypropylene has this tendency, especially at low temperatures as would be encountered in warehouses during storage. It can therefore be appreciated that in seeking a plastic sheet stock materials to satisfy all the requirements as suitable divider stock for multi-unit packages, there seemingly is no easy answer.